/* Filename: rcver.c
 * Description: 报式socket数据包变长
 * Last modified: humble 2021-11-12 09:36
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include "proto.h"

#define IPSTRSIZE (40)

static void usage(void);

int main(int argc, char **argv)
{
    int sd;
    int size;
    struct sockaddr_in laddr,raddr;
    struct msg_st *rbufp;
    socklen_t raddr_len;
    char ipstr[IPSTRSIZE];

    if(argc != 1){ fprintf(stderr, "argc !=1"); usage(); exit(1); }

    size = sizeof(struct msg_st) -1 + NAMEMAX;
    rbufp = malloc(size);
    if(!rbufp){ perror("malloc()"); exit(1); }

    sd = socket(AF_INET, SOCK_DGRAM, 0/*IPPROTO_UDP*/);
    if(sd < 0){ perror("socket()"); exit(1); }

    laddr.sin_family = AF_INET;
    laddr.sin_port = htons(atoi(RCVPORT));
    inet_pton(AF_INET, "0.0.0.0", &laddr.sin_addr);

    if(bind(sd, (void *)&laddr, sizeof(laddr)) < 0){ perror("bind()"); exit(1); }

    /* 重要：若没初始化该值，则会导致第一次收到数据出错 */
    raddr_len = sizeof(raddr);

    while(1){
        recvfrom(sd, rbufp, size, 0, (void *)&raddr, &raddr_len);
        inet_ntop(AF_INET, &raddr.sin_addr, ipstr, IPSTRSIZE);
        printf("---MESSAGE FROM:%s:%d---\n", ipstr, ntohs(raddr.sin_port));
        printf("name:%s\n", rbufp->name);
        printf("math:%d\n", ntohl(rbufp->math));
        printf("chinese:%d\n", ntohl(rbufp->chinese));
    }

    free(rbufp);
    close(sd);
    return 0;
}

static void usage(void)
{
#define USAGE "Usage:\n\
  Helloworld\n"
    printf(USAGE);
}
